Preheat oven to 220C/450F/gas7. Remove any stray feathers or quills from poussins. Wash and pat dry. Loosen skin over breast bones and work half softened butter over meat under skin. Season poussins inside and out. Trim and chop spring onions. Mix with half lavender. Divide between poussin cavities. Melt remaining softened butter in a skillet and seal birds on breasts. Turn until browned and sealed all over. Remove poussins and add the roughly chopped vegetables to brown them. Put the vegetables in the roasting tin and strew with the remaining lavender. Sit the birds on top, breast side down. This keeps the breast moist during cooking. Roast for 10 minutes. Turn the birds. Baste and then turn and roast for a further 10 minutes. Rest in a warm place for 15 minutes. Sauce: Add red wine to the roasting pan containing the vegetables and lavender. Deglaze the pan and reduce by half. Add the chicken stock and reduce again, pressing out all the sediment from the vegetables. Sieve into a clean pan. Whisk in the chilled butter to thicken and give it a gloss. Taste and season. Serve with the spring cabbage, hazelnuts and bacon and some buttered new potatoes scattered with chives for a very spring time dish!